gobi bat project and acoustic detection of bats

Gobi Bat Projectand

Acoustic Detection of Bats

Cori LausenBirchdale Ecological Ltd.

www.batsRus.ca

Great Gobi Strictly Protected Area Bat Project

Main Goals of Project:

1. To determine what species of bats are in the GGSPA using mistnets and bat detectors.

2. To record echolocation (bat ultrasound) from each species to know what each bat sounds like for identification without mistnet capture.

3. To teach Mongolian biologists about bat acoustics and how to use the bat detectors to learn more about bats in Mongolia.

Great Gobi Strictly Protected Area Bat Project May 2011

BAT DETECTORS: ANABAT and SM2BAT

Bat Detectors and Software Donated to Mongolia:

Titley Scientific (Australia) - Anabat

Wildlife Acoustics (USA) - SM2BAT

Joe Szewczak (USA) – Sonobat (analysis software)

Two Types of Detectors

Wildlife AcousticsSM2BAT

Titley ScientificAnabat

Full spectrum

Zero-crossing

Species of bats captured in Gobi

Vespertilio murinus

Species of bats captured in Gobi

Eptesicus gobiensis

Species of bats captured in Gobi

Hypsugo alashanicus

Species of bats captured in Gobi

Myotis mystacinus

Species Differences at a Glance

Vespertilio murinus

Eptesicus gobiensis

MINIMUM FREQUENCIES OF PULSES

Hypsugo alashanicusMyotis mystacinus

Species Previously Known from Great Gobi Strictly Protected Area

Recorded but not captured May 2011

Photo: Ariunbold

Plecotus kozlovi

Water as a Limiting FactorStudies in the Southwest USA (Rick Adams) have shown that bats do not move when their water source dries out, they just stop reproducing each year.

This means we need to keep checking for reproduction in dry areas with ephemeral water.

Enhancing Gobi’s water sources would be good for bats… it is currently being considered for bears (e.g. at Baran Tooroi).

Khulan Holes-keeping water open for bats

Making Bat-Friendly Water Troughs

• A way for them to crawl out of water (or they will drown)

• Appropriate size for all species of bats to benefit

Understanding bat echolocationWe can’t hear bats.

Frequency of sound:Humans hear <20kHz Speech is <5

kHz

Most bats echolocate >20kHz (ultrasound).

We therefore need to transform ultrasound into a lower frequency using bat detectors.

Sound• Sound is a wave.

Sound bounces off of objects providing echoes.

Object must be larger than one wavelength to reflect sound.

Sound

A 35 kHz frequency has a wavelength of ~1 cm, and would therefore best detect this size of object.

• Sound is a wave.

Sound bounces off of objects providing echoes.

Object must be larger than one wavelength to reflect sound.

Wave Length

• Wave length Increases as frequency decreases– 35kHz wave length = 10 mm– 70kHz wave length = 5 mm

• Shorter wavelengths (Higher Frequencies)– Can detect smaller objects– Provide finer detail

• Longer wavelengths (Lower Frequencies)– Travel further (Less absorbed by the air)

Example of ultrasound from Gobi Bats….

Freq

uenc

y (k

Hz)

Time (s)

35 kHz allows bat to detect objects 1 cm.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Clutter:-trees-grass-ground-other bats-detector-insect prey etc.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Clutter:-trees-grass-ground-other bats-detector-insect prey etc.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Clutter:-trees-grass-ground-other bats-detector-insect prey etc.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Clutter:-trees-grass-ground-other bats-detector-insect prey etc.

Freq

uenc

y (k

Hz)

Time (s)

Properties of bat echolocation. The effect of CLUTTER.

Clutter:-trees-grass-ground-other bats-detector-insect prey etc.

In High Clutter:

• Species/genera/families often converge– High slope– Short duration– Long frequency sweeps– Raised frequency

Clutter … makes identification of some species challenging

Little Brown in low clutter

Northern Myotis(a bat that tends to stay in high clutter)

Little Brown in high clutter

Mexican Freetail Bat

Big Brown Bat

• Two species of different families

• Produced at different levels of clutter

• Variation within an individual is much greater than between families!

Search-phase Continuum

Freq

uenc

y (k

Hz)

Time (s)

Feeding Buzz

Tadarida brasiliensis

Eptesicus fuscus

• Two species of different families

• Produced at different levels of clutter

• Variation within an individual is much greater than between families!

Search-phase Continuum

SLIDE BY C. CORBEN, ANABAT WORKSHOPS

To Understand Species Diversity in Mongolia

Collect reference calls from captured bats

-bat distributions can then be determined using bat detectors

-capture may not be required in many places of the country if a good reference call collection is established

-to evaluate whether taxonomic classifications are accurate, recording ultrasound from potentially cryptic species is important (e.g. Soprano vs Commom Pipistrelles in Europe)

Obtaining Reference Calls from Captures

• Hand-released *• Zip-lining• Bat-kiting

*Try to obtain ‘free-flying’ calls so wait until the bat has flown out of the hand but is still within recording distance of microphone. Ideal if they circle back over you, or you can run after them!

Reference Calls from BatsTethering Techniques

Zip-line

Bat-kite

Effects of Releasing a Bat

Analook View Unknown and Reference Files

SonobatView Unknown and Reference Files